GJ 1289 b

Astrophysical Synthesis & Habitability Characterization

GJ 1289 b is a confirmed sub-neptune exoplanet orbiting the star GJ 1289, located approximately 27.2 light-years (8.35 parsecs) from the Solar System. First announced in 2024 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.38 Earth radii and has a measured mass of 6.27 Earth masses. Combining its mass and radius yields a mean bulk density of 2.56 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.11 g⊕ (10.89 m/s²), and an escape velocity of 18.2 km/s.

In its orbital architecture around GJ 1289, GJ 1289 b completes one full revolution every 111.74 Earth days at a semi-major axis of 0.27 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 26.3 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.

❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 150 K (-123°C / -189°F) and an incident flux of 0.08 S⊕ (~103 W/m²), surface water and volatile species on GJ 1289 b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.

The host star GJ 1289 is classified as a low-mass red dwarf of spectral type M4.5 Ve with an effective photospheric temperature of 3,296 K, a radius of 0.245 R☉, a mass of 0.21 M☉, an estimated bolometric luminosity of 0.00636 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, GJ 1289 shines at apparent V-band magnitude 12.48 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

Discovery Facility: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).